The invention concerns a process, and an article made by the process, for the adhesive metallization of polyimide by pretreatment of the polyimide and subsequent activation as well as chemical and, if necessary, galvanic metal deposition.
It is known that for the purpose of metallization of non-conducting articles, processes for chemical metallization should be used.
In order to obtain sufficiently greater adhesive strength, it is necessary to roughen the surface of these articles mechanically or chemically. This occurs with many plastics, mainly by acid oxidative digestion of the surface, which is not, however, usable with plastics based upon polyimide.
This is a great disadvantage since polyimide foils advantageously find use in the electronics field in increasing measure, instead of glass fiber mats impregnated with epoxide resin. Polyimide foils are given consideration, namely, copper coated on both sides, for multi-level circuits, for example so-called multilayers, since they provide considerably better insulation values.
The application of the copper must generally be done by means of a suitable adhesive, since polyimide, in contrast to the plastics based upon epoxide resin, is not able to adhesively connect rolled on copper, which results in unfavorable working characteristics. Thus, upon boring of such multilayers, cavities form, which after the following metallization at the temperature of the adhesion process (about 250.degree. C.) can destroy the throughcontacting, or else adhesive residue must be removed, which of necessity is done by means of highly concentrated chromic acid.